1. Field of the Invention
The present invention relates to a method of regenerating a semiconductor wafer which is used during manufacture of a semiconductor device.
2. Description of the Background Art
Conventionally, regeneration of a semiconductor wafer has been practiced by performing processes of polishing, surface treatment and the like on a used wafer, to reuse the used wafer as a regenerate wafer.
However, a dummy wafer or a monitor wafer (i.e., a wafer used for various tests which does not have an actual integrated circuit formed therein) has been manufactured with a crystal defect therein such as a COP (crystal originated particle) being uncontrolled. Accordingly, in accordance with the conventional practices, regeneration of the dummy wafer would expose a crystal defect such as a COP formed in a substrate of the dummy wafer in a surface of the dummy wafer, or newly produce a crystal defect such as a COP in a surface of the dummy wafer, due to a polishing process or the like required for the regeneration. As such, there has been a problem that a regenerate wafer obtained by regenerating a dummy wafer or the like is of no practical use.
FIG. 9 is a view schematically illustrating an example of a COP. FIG. 9 shows that a regenerate wafer 11 to which a conventional method of regenerating a semiconductor wafer has been applied has a COP 12 exposed in a surface thereof.
FIG. 10 is a view schematically illustrating another example of a COP. FIG. 10 shows that a regenerate wafer 21 to which the conventional method of regenerating a semiconductor wafer has been applied has a COP 22 produced in a surface thereof.
It is an object of the present invention to obtain a method of regenerating a semiconductor wafer which allows a used wafer, even if the wafer contains a crystal defect such as a COP, to be regenerated into a high-quality semiconductor wafer.
A first aspect of the present invention is intended for a method of regenerating a used semiconductor wafer in which a surface coating layer including a metal film and an insulating film is formed at least in a surface thereof. According to the present invention, the method includes the following steps (a) to (d). The step (a) is to polish the surface of the used semiconductor wafer. The step (b) is to immerse the used semiconductor wafer after the step (a) in mixed acids including at least two kinds of acids. The step (c) is to perform a surface treatment on the used semiconductor wafer after the step (b). The step (d) is to perform an annealing process on a quasi-regenerate wafer which is the used semiconductor wafer after the step (c).
The annealing process on the quasi-regenerate wafer in the step (d). This makes it possible to significantly reduce crystal defects remaining in the quasi-regenerate wafer. Accordingly, a high-quality regenerate wafer can be obtained after the step (d).
A second aspect of the present invention is intended for a method of regenerating a used semiconductor wafer in which a surface coating layer including a metal film and an insulating film is formed at least in a surface thereof. According to the present invention, the method includes the following steps (a) to (d). The step (a) is to polish the surface of the used semiconductor wafer. The step (b) is to immerse the used semiconductor wafer after the step (a) in mixed acids including at least two kinds of acids. The step (c) is to perform a surface treatment on the used semiconductor wafer after the step (b). The step (d) is to cause a quasi-regenerate wafer which is the used semiconductor wafer after the step (c) to epitaxially grow to form an epitaxial growth layer, thereby obtaining a regenerate wafer including the quasi-regenerate wafer and the epitaxial growth layer.
The epitaxial growth process in which the quasi-regenerate wafer is caused to epitaxially grow to form the epitaxial growth layer in the step (d). This makes it possible to significantly reduce crystal defects remaining in the quasi-regenerate wafer. Accordingly, a high-quality regenerate wafer can be obtained after the step (d).
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.